Mazz1972, looks like you have received some good advice from other members.
I believe the blue/white warrant you have is the MfE version (link http://www.mfe.govt.nz/issues/waste/freedom-camping/
). This means another issuing authority inspected your vehicle. Do you know the name of the issuing authority? Should be on the warrant. The Standard requirements haven't changed since 2001 so I am a little concerned that an issuing authority is signing these off when the recheck identified issues with plumbing.
The Standard is adminstered by the Ministry of the Environment (not NZMCA as many still believe), so anyone is welcome to contact an issuing authority to have their vehicle inspected. The NZMCA has extended its inspection services to non-members for a very long time, but only recently have we decided to advertise it.
On the green sticker, members are correct that it is not complusory under the Standard (yet!). It was created in Nov2008 to assist enforcement officers identify from a distance those that are CSC without having to refer to the warrant and peer through the front windscreen. If you can, it's better to display one (on the rear) to make it easier for the enforcement officers and yourselves. Otherwise you may get a knock on the door every time you park up. We are working on a proposal to amend the Standard and adopt the green sticker (or something similar to it).